A particular area of application of a padlock is in the field of occupational safety. There is the risk in connection with the servicing of industrial plants, for example, of a production machine, that the industrial plan deactivated for the purpose of service work is activated again by accident while the servicing work is still continuing. A substantial danger for the service engineer can result from this. It is therefore customary that the service engineer moves a switch associated with the industrial plant to an OFF position for the duration of the service work and secures it in this position, i.e. the switch is directly blocked or access to the switch is blocked. The named switch is typically an energy supply switch, for example a main electrical switch of a control device or of an energy supply device of the industrial plant (e.g. power switchbox). Alternatively to this, the named switch can, for example, be a valve of a liquid line or of a gas line.
In order effectively to avoid an accidental activation of the industrial plant by another person, each service engineer hangs a padlock on the named switch or on a blocking device associated with the switch before starting his work and locks said padlock. The switch is hereby secured in its OFF position, i.e. the switch cannot be moved accidentally back into an ON position by another person. When the service engineer has ended his work, he unlocks his padlock again and releases it from the switch. Each service engineer usually has his own individual padlock (or a plurality of his own individual padlocks) associated with him.
This procedure is also called locking out. The padlock used is accordingly called a lockout lock. The document U.S. Pat. No. 5,449,867 shows such a securing of an electric rocker switch by means of a padlock. It is known from the document U.S. Pat. No. 3,171,908 to secure the position of a rotary switch by means of a padlock.
So that a plurality of service engineers can block and release the switch again independently of one another, a plurality of receivers (e.g. eyelets) can be provided at the switch for hanging a plurality of lockout locks. This is known from the document U.S. Pat. No. 6,388,213, for example. If only a single receiver for a lockout lock is provided, a securing claw can be used which is hung into the respective eyelet of the switch or of the associated blocking device and which in turn has a plurality of hang-in eyelets for a respective padlock. Only when the last padlock has been removed from the securing claw can the securing claw be removed from the switch so that it can again be brought into the ON position. Such a securing claw for use at an electric switchbox is known, for example, from documents U.S. Pat. Nos. 6,396,008, 5,365,757 and 3,667,259.
It is known in connection with such a securing of a switch of an industrial plant to equip the lockout lock used with a housing of plastic, with a hoop being displaceably held at the lock housing and with a lock cylinder being arranged in the lock housing. The lock cylinder can selectively be brought from an open position into a locked position to lock the hoop to the lock housing after the hoop has, for example, been hung into an eyelet of the switch. By forming the lock housing from plastic, a particularly light padlock results which is of advantage in the use as a lockout lock since the service engineers occasionally carry a plurality of lockout locks simultaneously. A housing of plastic can also contribute to a desired electrical insulation. By the use of a plastic housing, there is furthermore a particularly simple possibility of color marking the padlock. The smaller stability of a plastic housing in comparison with a lock housing made of metal does not represent any serous disadvantage in a lockout lock since the padlock only serves the purpose of securing a switch against unintentional actuation, but not, for example, as theft protection. Such a lockout lock having a housing of plastic is known, for example, from documents U.S. Pat. Nos. 7,278,283 and 5,755,121. They are here cases of simple, purely mechanical padlocks.